The company says it has raised $120 million in initial financing—a huge sum for a startup using technology built from scratch. One major backer is Seattle-based Arch Venture Partners. Managing Director Bob Nelson says he’s lost money on other immunotherapy gambits, but Juno’s early results convinced him to make the biggest investment in the firm’s history.

“When you start looking at CT scans of people that have stage-four cancer and then it goes away in two weeks, you get excited,” Nelson said.

Much more testing is needed on those promising early results, however.

And there are more reasons to be skeptical. Other much-hyped biotech ventures, such as Seattle’s Dendreon, have delivered what many consider disappointing results. And cancer cells are unpredictable and notoriously clever at morphing to evade new treatments.

But if it succeeds, Juno’s technology could change the outlook for people in the late stages of many different cancers.